Answer:
E. threat to native species of plants and animals as well as to maintaining biologically diverse ecosystems, after losing their habitat
Well there are many catastrophic scenarios that we already overcome. You should consider educating yourself about the great filter. A great filter is a hypothetical barrier that each civilization can or cannot overcome. From here on things get a little complex so I won't bore you with them. But there are experts in this theory called great filter and I'm sure they can tell you a lot about.
Answer:
I'm almost positive it's answer c. :)
Hectares of land used per person